Optically induced reorientational aggregation and the stability of F(2)(+) color-center lasers

Spectroscopic evidence is presented showing that F(2) centers in KCI optically convert to an array of higher Faggregate centers at temperatures as low as 40 K. This aggregation occurs through random diffusion of F(2)(+) centers by means of repeated optical reorientation. Stable lasing of the F(2)(+) center has been achieved at a crystal temperature below which this reorientational aggregation ceases.